<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <button id='ldh'>刘德华</button>
    <button id='zxy'>张学友</button>
    <br>
    <img src="images/ldh.png" alt="" title="刘德华">

    <script>
        var ldh = document.getElementById('ldh');
        var zxy = document.getElementById('zxy');
        var img = document.querySelector('img');

        zxy.onclick = function () {
            img.src = 'images/zxy.png';
            img.title = '张学友';
        }
        ldh.onclick = function () {
            img.src = 'images/ldh.png';
            img.title = '刘德华';
        }
    </script>
</body>

</html>